Inhibitor and process employing the same



252. COMPOSITIONS.

- and the like.

Patented June 23,1936

,UNITED STATES Cross Reference PATENT OFFICE I t INHIBITOR AND PROCESS EIHPLOYING me a. Sheibley, Cleveland Heights, Ohio, as-

signer to The Grasselli Chemical Company,

Cleveland, Ohio, a corporation of Delaware No Drawing. Application February 2, 1935., Serial ,631

, 16 Claims. (01. ue-ai) Pickling and metal cleaning operations irequently involve the use of a bath of dilute, nonoxidizing acids such as "sulfuric, hydrochloric, acetic, formic, aqueous solutions of acid sulfates, Such baths are used for numerous purposes, a typical example of which is the pickling of iron or steel articles such as wire, sheet, and other manufactures. The composition, concentration. temperature of operation, and other factors vary with different baths, but. in every instance the primary function of a bath is the re-v moval of undesirable incrustations. As soon as the base metal becomes exposed, it is, in the absense of 'an inhibitor, attacked by the bath with consequent damage to the article and with an unnecessary consumption of acid.

The application of my invention to acid pick ling and acid metal cleaning operations involves no changes in the customary baths and processes, except for the addition of a small amount of the inhibitors of this application. In quantities as small as one-hundredth of one per cent, my novel inhibitors will check the attack of acid on metal. I usually prefer to employ between about twohundredths of one per cent and one-tenth of one per cent of one of-my inhibitors, but more or less may be used if desired. The compounds discussed hereinafter were tested by using one-hundred and twenty-five ten thousandths, of a per cent, based on the weight of the bath, in a five per cent sulfuric acid solution.

It will, of course, be apparent that my nove inhibitors may be used in numerous other relations as have the inhibitors already known to the art. I

I have found very satisfactory as' inhibito compounds which contain thegroup;

practice, and in accordance with the terminology used herein.

The inhibitors of my invention may, for lack of better terminology, be designated as deriva-- tives of quinazoline which contain the above in- 5 dicated nucleus (1).. It will be understood, of course, that while thecompounds may all conceivably be derived from quinazoline, it is frequently more practicable to prepare them from other compounds. 10

In one broad aspect, my invention contemplates the use of compositions of the formula:

V Bi N 3| l5 in which the valence at R: is satisfied by hydrogen, ammonovalent organic group, or else the valence is satisfied by the carbon in the 2-position; in which the valence at R: is satisfied by a 25 monovalent sulfur-containing group, a monovalent oxygen-containing group, a monovalent organic group, hydrogen, by linkage to nitrogen in thel-position, or satisfied, together with the valence at B3, by oxygen, sulfur, or a divalent organic group; in which the valence at Rs, if not satisfied together with R2, is satisfied by or monovalent sulfur-containing group, an amino group, a monovalent oxygen-containing group, a monovalent organic group, or by hydrogen; in which the valence at B4 is satisfied by hydrogen, an amino group, a monovalent organic group, by linkage to the 4-carbon, or, if the N is pentavalent, by linkage to the 4'-carbon and by the cation and anion of an acid; in which the valence at Re is satisfied by a monovalent sulfur-containing group, a monovalent oxygen-containing group, a monovalent organic group, hydrogen, linkage to the nitrogen in the 3-position, or satisfied, together with the valence at Re, by oxygen, sulfur, or a di-valent organic group; in which the valence at Ralf not satisfied together with Rs, is satisfied by a monovalent sulfur-containing group, an amino group, a monovalent oxy-, gen-containing group, a monovalent organic group, or hydrogen; and in which the valences at B1, Re, Ru. and Rm are satisfied by substituents for the hydrogen of the benzene ring, or by the hydrogen of the ring.

Exerciser o r g A 20.

UI USS HUIUI UIIUU i252. COMPOSITIONS. v Examine,

bers of thislarge class of compounds wfllbe disas efiicient as it would be in its refined, but 7 cussed in detail hereinafter.

Generally speaking, quinazoline derivatives of the type of Formula (2) are most efiective as l inhibitors when they contain sulfur. A few exceptions to this statement will be discussed in detail hereinafter, and, as will then be noted.

2,4 dianilinoquinazoline 0,0 dicarboxylic acid dimethyl ester hydrochloride, particularly, is an 10 astonishingly excellent inhibitor despite the fact that no sulfur is present.

It is usually preferable to locate the sulfur in the 2-position. The 4-position is more reactive, and the sulfur, if at the 4-position, is more sus- 15 ceptible to oxidation and hydrolysis. Compounds wlth sulfur in the 2-position are fairly easily made, and they are relatively stable.

Oxygen and hydrogen are more easily retained in the 4-position, as are organic groups. How- 2 ever, in view of the greater reactivity of the 4- position, it is generally preferable to locate organic groups in the 2-position, unless, of course. it is desired to have organic groups in both.

In choosing between the 1-position and the 25 3-position, it is preferable to locate a given group in the 3-position. A compound with a given group in the 3-position is usually more easily dispersed than a similar compound with the given group in the l-position. For instance, 2-

30 thio-3-allyl-4-ketotetralnvdroquinazoline is an excellent inhibitor, easily soluble in acetone, and readily dispersible in an acid bath; while l-allyl- 2-thio-4-ketotetrahydroquinazoline is a somewhat poorer inhibitor by reason of the difllculty 35 experienced in dispersing it in an acid-bath. For

purposes of comparison, the formulae of the compounds are given herewith:

n a n n-g-c=-on 2-thio-3-allyl-4-ketotetrahydroquinasolinen n n -c=on n 50 NC=S 1 i4) I l-allyl-2-thio-4-ketotetrahydroquinazoline- Various groups may be located at the 5-, 6-, 7-, and a-positions with considerable success. One or more alkyl or aryl groups may be sub- 50 stituted on the benzene ring, and, if desired, one or more carboxyl groups may be similarly'located, Other substituents such as nitro-groups, -SH, etc., may likewise be used. Generally speaking, I prefer not to substitute halogen on the benzene 65 ring, for, as will be seen hereinafter, such compounds are not overly satisfactory as inhibitors. Generally, I prefer to employ my compounds in as pure a state 'as is commercially feasible, because, as will be pointed out hereinafter, crude,

70 impure products do not have as great an inhibiting efilciency as do the purified products. It will be understood, however, that I do not limit myself to purified products, because, in many cases, it may be economically desirable to use 75 a less expensive product even tho it is not quite more expensive form.

My novel inhibitors may be dispersed in acid baths in any suitable manner. Some are not readily dispersible, and it is preferable to add 6 such compounds to a bath after first dispersing (or dissolving) them in a suitable solvent. Most of the compounds discussed herein were tested by dispersing them in acetone, tho, in some cases, other methods were found more suitable. In 10 connection with my specific examples, given hereinafter, I shall indicate the methods of dispersion used with each compound. It will, of course, be readily apparent that any suitable method of dispersion may be employed, and numerous ways will readily occur to those skilled in the art. Besides using suitable solvents for the inhibitors, they may be dispersed for example, by adding suitable dispersing agents such as gum arabic, Goulac, saponin, and the like. Many of the compounds of my invention are readily dispersible in an acid bath by simply adding the compounds to the bath, and no particular attention is required as to their method of addition.

In alkaline solution some of my compounds undergo a desmotropic conversion with the formation of alkaline salts. I may use such compounds in the form of their alkaline salts, but I generally prefer not to. It would be expected that in an acid bath the original compound would be regenerated. but in some cases this is not entirely true. It will be noted hereinafter, in connection with specific examples, that certain of the compounds of my invention are not as desirable as inhibitors when added to an acid bath 'in alkaline solution.

A little more specifically considered than in Formula (2), my inhibitors are comprised of compounds of the formula:

- in which the valence at R; is satisfied by hydrogen, an alkyl, aryl, or aralkyl group, or else the valence is satisfied by the carbon in the 2-position; in which R: is satisfied by the nitrogen in the 1-position, or by hydrogen, an alkyl, aryl, aralkyl, alkoxy, aryloxy, amino, arylamino, or alkylamino group, or satisfied, together with the valence at Ra. y Oxygen lfur; in which the valence at Rs, if not satisfied together with the valence at R2, is satisfied by hydrogen, an alkyl, aryl, arallwl, alkoxy, aryloxy, amino, arylamino, or alkylamino group; in which the valence at R4 is satisfied by hydrogen, an alkyl, aryl, aralkyl, amino, arylamino, oralkylamino group, or by the valence at Rs; in which the valence at Rs is satisfied by the nitrogen in the 3-position, or by hydrogen, an aryl, alkyl, aralkyl, alkoxy', aryloxy, amino, arylamino, or alkylamino group, or satisfied, together with the valence at Re, by sulfur or oxygen; 'and in which the valence at Rs, if not satisfied together with R5, is satisfied by hydrogen, an alkyl, aryl, aralkyl, alkoxy, aryloxy, amino, alkylamino, or arylamino group. In one rather specific aspect of my invention, I contemplate the use of a group of compounds which may be designated as derivatives of normal, or unreduced, quinazoline. This group of compounds has the following formula:

(o I o in which the valence at R1 is satisfied by hydrogen, or by an alkyl, aryi, aralkyl, alkoxy, aryloxy, alkylamino, or arylamlno'groupi in which the valence at R: is satisfied bydiydrogen, or by an alkyl, aryl, aralhyl, alkoxy, aryloxy, alkylamino, or arylamino group; and in which; and y are the cation and anion of an acidif the nitrogen in the 3-position is pentavalent.

The simplest member of this group is quinazoline itself, in which R1, and R: are both hydrogen. Quinazoline is a crystallineholid which melts at 48' C., and which is very soluble. when a small amount of quinazoline was added to.- a sulfuric acid bath, it was found to be none too satisfactory an inhibitor.

. No. a. I a,

cies as inhibitors under the specific conditions noted herein.

Tsnnl Formula ('7). 4

8, is probably similarly located, and, for the pur- This compound was prepared by reacting 2,4- dichloroquinazoline with methyl anthranilate. It has a melting point of 261' C. The position of attachment of the hydrogen chloride has not been directly demonstrated, but from the empirical evidence available to me, it seems most probable that the HCl is located as shown in The HCl in Compounds 6. 7, and

poses of this application, I shall refer to such acid containing products as salts.

As is noted in Table 2, 2,4-dlanilinoquinazolineo,o'-dlcarboxylic acid dimethyl Y ester hydrochloride was added to a sulfuric acid bath in acetone solution with excellent results. Although this compound contains no sulfur, it displayed an exceedingly great emciency as an inhibitor. By the standard lossv of weight method of determination, this compound was formal to have an efllciency only a fraction of a per cent below 100%.

The Compound 7 of Table 2, 2,4-dianilinoquin-' azoiine m,m'- dicarboxylic acid hydrochloride, and Compound 8, 2,4-dianilinoquinazoline-p,p'- dicarboxylic acid hydrochloride, proved less emcient than Compound 5, probably in part because of their poorer dispersion.

The Compound 1 of Table l, 2,4-dianilinoquinazoline, was found to be about as ,efilcient as Compounds 7 and 8 under the conditions of the tests. The Compound 4 of Table l, 2,4-diethoxy- 'quinazoline, despite its good dispersion in the sulfuric acid bath, was the poorest inhibitor o1! Emmples of eempounds according to Formula (6) Appearance Mode of addition to both Small white n Small pale yellow needles In acetone: Poor dispersion. Small, white glistening plat'es.... in acetone: Good (I Orange brown eioidcelglsles Directto can; with? 10s., In acetone: Good dlspcsfl Tana: 2

Additional examples of cmnpozmds of Formula (6) :Contatnina HQ! Appeuance Mode of addition to I bath de-raou 0-NHCeH4COOOHs-...

ana.

m-Nnc.m0oon..

-nnctmcoon Yellow, crystalline pow er. Pale yellow powder..-

lneeetone: Gcoddisispcs n. Pale yellow powder... InPconc. sulfuric acid:

oor dispersion.

The best of the inhibitors of this group ls'No. 5. This is 2,4-dianilinoquinazolineo,o'-dicarboxylic acid dimethyl ester hydrochloride, which has the following formula:

l vention, I contemplate the use, as inhibitors, of

compounds which may be designated as deriva- I tives of 4-ketodihydroquinazoline. This group of compounds has the formula:

yer-4h m which the valence at a. a satisfied by hydrogen, or by an alkyl, aryl, aralkyl, alkoxy, aryloxy. alkyiamino, or arylamino group; and in which the valence at R: is satisfied by hydrogen, or by an alkyl or aryl group.

Lita-rhea...

"p52. COMPOSITIONS In the following table are listed a number of examples of compounds of the type of Formula i (8). As in Tables 1 and 2, the compounds are 5 listed in approximately the decreasing order oi' 6 their efilciencies:

Teens 3 Examples of compounds according to Formula (8) No. RI R, Appearance &:

9 CH=CHC.H|. H... Fine, white In hot alcohol: needles. Good on. 10 CsHl H.-- e. chalky In .aoetone Good needles. persion. 11 H H--. Asbestos like In acetone: Good needles dispersion. l2 OCeHI H..- Fine, white In acetone: Good needles. dispersion. i3 OCH; CH; Fine, white In acetone: Good needles. persion. 14 003B; H... Long, slandc' In acetone: Good needles. dispersion. l5 NHCJI. H--- Crude product In cone.

used. acid: Good dis- The compounds of this group are, generally, lower in eiiiciency than the compounds. of Formula (6). The Compound No. 9, 2-styryl-4-ketodihydroquinazoline, has the following formula:

' This compound is the most satisfactory inhibitor of this group, and I believe that it is the presence of the unsaturated side chain which causes the compound to be better than others of this group. One of my preferred inhibitors, noted hereinafter, likewise contains an unsaturated side chain.

The compound 11, d-ketodihydroqulnazoline is not overly efilcient as an inhibitor, but it may sometimes be found efl'icient enough for particular uses. It can assume an enolic form thus:

Br ll:

Cross Reference in which the valence at R1 is satisfied by hydrogen or by an alkyl group; in which the valence at R: is satisfied by hydrogen, or by an alkyl, aryl, or aralkyl group, in which the valences at Ra, R4, and Re are satisfied by the hydrogen of the benzene ring, or by nitro groups, halogen groups, or carboxylic acid groups; and in which the valences at :r are satisfied by oxygen or sulfur.

In the following table are listed a number of examples of compounds of the group of Formula (11) in which a: is ongen. The compounds are listed in approximately the decreasing order of their effectiveness:

Tanm4 Examples of compounds according to Formula (11) Modeoiaddi- No. R; R aRnd Rs Appearance flontobam 16 H H H H Small white In oonc. sulneedles iurio acid: good disper- 17 H H N0 11 Yellow In cone. sulprisms iurio acid:

(:ood disperson.

01K; OH; H I! Fine. white In acetone:

on. H H H 0008 Crystalline In oohc. sulpowdar [uric acid: I s(:ood dispuon. so 0H4 03H] H H Fine, white In acetone: y needles (iood disper- SOIL 01H. H H Granular. In alcohol:

white crys- Good dispertals sion. H H Br Yellownee- In conc. suldles (uric acid:

Poor pc- I sion.

8 H C|H| Br H Glistening, In cone. enlwhitenee- (uric acid dies oor dispersion.

- droquinazoline-S-carboxylic acld with the following formula:

The halogen substituted Compounds No. 22, ssdibromo-2,4-diketotetrahydroquinazoline, and No.

Examiner I, 3,014,900 1 S 23, 3-ethyl-6,8-dibromo-2,4- diketotetrahydro- .the 3-phenyl-2,4-diketoteline is quinazoline, are exceedingly poor inhibitors, and, slowly converted, and, therefore, is slowly soluble whileIintendtocovertheminmyelaimaTdo inalkali.

not prefer to use them in most relations. These compounds have the formula:

3-ethyl-6,8- dibromo 2,4 diketotetrahydroquln azoline. v 7 Compound No. 16, 2,4-diketotetrahydroquin azoline, may be used in the form of its alkaline salts, for, like 4-ketodihydroqulnazoline, it can undergo a desmotropic transformation according to the following:

The presence of a group other than hydrogen on the nitrogen atoms will, of course, prevent a desmotropic conversion, and such compounds as No. 13, No. 18, etc. are not alkali soluble, and will 20 not form salts with alkaline agents. The compounds of the type of Formula (8) do not contain a carbonyl group. and. of course, they have no enol form.

A large number of the compounds of my invention are alkali soluble, and they may be added to an acid bath in the form of their salts. As further examples, I may note Compounds No. 9, No. 10, and No. 17. 30

While I may add my compounds in the form of their alkaline salts, if any. I usually prefer not to. One would expect the salts to be converted to the original compound, but, as will be noted hereinafter, some of my compounds are less satisfactory 85 when used in the form of their sodium salts.

Among the most efilcient and most satisfactory of my novel inhibitors, are the compounds of Formula (11) y when x is sulfur. The compounds 40 When 2,4-diketotetrahydroquinazo1ine (15a) is now to be discussed are included in the discussion put in alkaline solution, it is converted to the of Formula (11). an 88 I 1 l this. 8 '0"? desmotropic forms (15b) and (15c). The hymay be regarded, rather specifically, as derivadroxyl group in the active 4-position is acidic, and tives of 2-thio-4-ketotetrahy r q of the the compoundwill form alkaline salts. When formula: 55 2,4-diketotetrahydroquinazoline is put in a sodium hydroxide solution, for instance, the followingcompounds form:

c=-0 0-011 m z-s (10) i -n.

t; 8 on a *Na a in which the valence at B1 is satisfied by hydrogen or by any alkyl group; and in which the va-' lence at R: is satisfied by hydrogen, or by an alhl, aryl, or aralkyl group. 70

A few examples of compounds according to Formula (18) are given below in approximately the decreasing order of their efllciencies. Under' the heading "Appearance" are noted the appearances of the compounds and the solvents from I2. COMPOSITIONS.

use

LJOSS with baths containing them, and as each was of high emcieney.

TAIL! 5 4 v Examples of compounds according to Formula (18) 5 No a, a, 1M fig? Modeoiaddltiontobath as n our. White, prlsmationaedmhomaloohol our 0... in acetone: Good dispcsion. m as n om. wgatacgfioniug plates: from glacial In acetone: Good dispersion. 26 H o-OEhCdh w lg t e ilsgening flakes: h-om glacial 205 C... In acetone: Good dispu-sioa. 27 H D-CHsCeHe W5 g l is teuiug platu from glacial Lnaoetone: Poor dilplsion. as on. 0.1:. Thin, opaque needleszirombensene 28 0-- Iumcsouc. sulfuric acid: Good 15 29 on. on. sum, white needles: hum .182" o-.. m cone. sulfuric acid: Good The above compounds were prepared by reactin: an appropriate alkyl or aryl isothiocyanate with anthranilic or N-methylanthranilic acid. Compound 24, for instance, was prepared by refluxing allyl isothiocyanate with anthranilic acid.

,Other methods of preparation may, obviously, be used The Compound No. 24, 2-thio-3-aJlyl-4-ketotetrahydroqulnazoline, gave the best results of any of the compounds tested, both from the standpoint of efficiency and from the standpoint of the brightness of the acid treated articles. This compound is shown below in its usual form (19a) and in its desmotropic conversion (19b) This compound formed sodium salts. but. pecullarly enough, when it was dispersed in a pickling bath by slowly adding a solution of it =ketotetrahydroquinazoline, was less eflicient than the purined product.

The Compound No. 25, 2-thio-3-phenyl-4-ketotetrahydroquinazoline, is one of my preferred inhibitors. It is readily dispersible in a pickling bath, and it is a very efficient inhibitor. It has the following formula:

The um four compounds in m. 5 were all found to be very satisfactory inhibitors, as each left an excellent, bright i'inish on articles In addition to the compounds falling in one 20 of the above groups, there are. of course, numerous. other compounds which fall within the scope of my invention. While, as is above noted,

I prefer to use compounds with sulfur, if any, in the 2-position, I may also use compounds with 25 sulfur in the 4-position. I may, for example, use compounds of the type of 2-methyl-4-thiodihydroquinazoline:

0gn A w as Another interesting compound which has sulfur in the 4-position in 2,4-dithiotetrahydroquinazoline:

Compounds of the type of Formula (21) and 48 (22) are not overly satisfactory because the sulfur in the 4-position is very susceptible to oxidation and hydrolysis.

The inhibitors of myinventlon may be employedin similar manner to the inhibitors known 60 heretofore. They may be sold in the form of impure commercial compounds, or in the form of relatively pure compounds. It may sometimes be desirable to sell mixtures of the compounds of my invention with each other or with known ll inhibitors. My inhibitors may, of course, be marketed as such, or they may be mixed with disper-sing agents and/or foaming agentssuch aa Goulae, saponin, soap bark, and gumarable. It may sometimes be found desirable to sell the Q inhibitor in a suitable solvent, or to sell it already mixed with acid.

While I have shown certain specific compositions and certain methods of preparing them, I do not intend to be limited thereby. It will be readily apparentto those skilled in the art that numerous equivalent compounds can be used. and that my compounds can be used alone or in various mixtures'ln numerous relations without departing from the spirit of my invention. The 10 scopeof myinventionis'setforthinthefollaw- I claim:

1. A pickling and cleaning composition com prising a non-oxidising acid and a composition 1| Exam-leer comprising a characterized comprisin 2-thio-3-allyl-4-ketotetrahydroquin- 'azoline.

3. A pickling and cleaning composition com prising a non-oxidizing acid and a composition comprising 2,4-dianilinoquinazoline o,o'- dicarhonlic acid dimethyl ester hydrochloride.

4. A pickling and cleaning composition comprising a non-oxidizing acid and a composition comprising 2-styryl-4-ketodihydroquinazoline.

5. In a process of treating metal, the step comprising subjecting the metal to the action of an acidic material inhibited by a composition comprising a material characterized by the presence of the group:

6. A pickling and cleaning composition comprising a non-oxidizing acid and a derivative of normal quinazoline characterized by the presence 01 the group:

d-ketodihydroquinazoline characterized by the presence of the group:

, thepresence oithegroup:

8.-A pickling and cleaning composition comprising a non-oxidizing acid and a derivative of 2,4-diketotetrahydroquinazolinecharacterized by o- A A GJY I 10 9. A pickling and cleaning compositioncom prising a non-oxidizing acid and a derivative oi. 15

' .2-thio-4-ketotetrahydroquinazoline characterized by the presence oi the group:

.10. In a process oi cleaning and pickling metals, the step comprising subjecting the metal to the action of a composition of claim 2. 3o

11. In a process of cleaning and pickling metals, the step comprising subjecting the metal to the action of a composition 0! claim 3.

12. In a process oi cleaning and pickling metals, the step comprising subjecting the metal to the 35 action of a composition of claim 4.

13. In a process of cleaning and pickling metals. the step comprising subjecting the metal to the action of a composition of claim 6. v v

14. In a process of cleaning and pickling metals,

the step comprising subjecting the metal to the m FRED 3. 8. w 

